Fine wiring pattern and composition, manufacturing method thereof, and thermal print head including fine wiring pattern

ABSTRACT

According to the present disclosure, a manufacturing method of a fine wiring pattern is disclosed. The manufacturing method includes preparing a support member, forming a first layer on the support member by thick-film printing, and forming a second layer including Ag on the first layer by the thick-film printing. The method also includes forming a predetermined fine wiring pattern by performing an etching process upon the first layer and the second layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application Nos. 2012-012936, filed on Jan. 25, 2012,and 2012-120888, filed on May 28, 2012, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a fine wiring pattern, a manufacturingmethod of the fine wiring pattern, and a thermal print head.

BACKGROUND

Conventionally, a thermal print head, which performs a printingoperation by applying heat to thermal paper or thermal ink ribbon, hasbeen proposed. For example, a thermal print head including an electrodelayer supported on a substrate and a resistor layer partially coveringthe electrode layer is disclosed. The electrode layer includes a commonelectrode having a plurality of gaps therebetween, and a plurality ofindividual electrodes. The resistor layer has a strip shape extending ina primary scanning direction to bridge the plurality of gaps of theelectrode layer. The electrode layer is formed by an electricalconductor mainly composed of Au. It is required that the electrode layeris suitably supported on a substrate, a resistance of the electrodelayer is reduced, the electrode layer is well contacted with theresistor layer, a wire used to connect an IC for controlling is wellbonded, and the like. As a configuration in response to such demand, theelectrode layer is formed by an electrical conductor mainly composed ofAu.

However, because Au is an expensive material, the manufacturing cost ofthe thermal print head is increased when Au is selected as a maincomponent of the electrode layer. In order to reduce the manufacturingcost of the thermal print head, it is desired that the demand for theabove electrode layer is satisfied and the electrode layer isconstructed with a lower cost.

SUMMARY

The present disclosure has been proposed under the circumstancesdescribed above. It is therefore an objective of the present disclosureto provide a manufacturing method of a fine wiring pattern, the finewiring pattern and a thermal print head, which can suppress themanufacturing cost and construct a suitable electrode layer.

A manufacturing method of a fine wiring pattern provided in a firstaspect of the present disclosure includes: preparing a support member;forming a first layer on the support member by thick-film printing;forming a second layer including Ag on the first layer by the thick-filmprinting; and forming a predetermined fine wiring pattern by performingan etching process upon the first layer and the second layer.

In some embodiments of the present disclosure, the fine wiring patternincludes a plurality of wire portions, and a space between the adjacentwire portions is equal to or less than 40 μm.

In some embodiments of the present disclosure, at least one portion ofthe fine wiring pattern has a wiring width of 25 μm or smaller.

In some embodiments of the present disclosure, the first layer and thesecond layer include Ag.

In some embodiments of the present disclosure, the first layer is formedthinner than the second layer.

In some embodiments of the present disclosure, the first layer includesPd.

In some embodiments of the present disclosure, the first layer and thesecond layer include Pd, and Pd content of the first layer is largerthan Pd content of the second layer.

In some embodiments of the present disclosure, the support memberincludes a substrate made of a ceramic and a glaze layer formed on thesubstrate.

In some embodiments of the present disclosure, the second layer includesAg particles.

In some embodiments of the present disclosure, the second layer includesa glass.

In some embodiments of the present disclosure, the first layer includesan organic Ag compound.

In some embodiments of the present disclosure, the step of forming thefirst layer is performed by using a first paste material including Ag ina first ratio, and the step of forming the second layer includes:installing a second paste material including Ag in a second ratio on thefirst layer to expose a portion of the first layer, and the second ratiois larger than the first ratio.

In some embodiments of the present disclosure, the first layer is mainlycomposed of an Ag—Pd alloy and the ratio of Ag is equal to or less than80%, and the second layer is mainly composed of an Ag—Pd alloy and theratio of Ag is equal to or more than 80%.

In some embodiments of the present disclosure, the step of performingthe etching upon the first layer and the second layer includes: forminga plurality of strip-shaped portions arranged along a first direction,and in the step of forming the second layer, the first layer is exposedin a strip-shaped region extended in the first direction.

In some embodiments of the present disclosure, the plurality ofstrip-shaped portions is formed to intersect the strip-shaped region ina second direction perpendicular to the first direction.

In some embodiments of the present disclosure, the step of forming thefirst layer is performed by using a first paste material including Ag ina first ratio, and the step of forming the second layer includes:installing a second paste material including Ag in a second ratio on aregion that is not covered by the first layer on the support member,wherein the second ratio is smaller than the first ratio.

In some embodiments of the present disclosure, the first layer is mainlycomposed of an Ag—Pd alloy and the ratio of Ag is equal to or more than80%, and the second layer is mainly composed of an Ag—Pd alloy and theratio of Ag is equal to or less than 80%.

A fine wiring pattern provided according to a second aspect of thepresent disclosure is formed by the manufacturing method of the finewiring pattern provided according to the first aspect of the presentdisclosure.

A thermal print head provided according to a third aspect of the presentdisclosure includes the fine wiring pattern provided according to thesecond aspect of the present disclosure.

In some embodiments of the present disclosure, the thermal print headfurther includes a drive IC; and a wire for connecting the drive IC andthe fine wiring pattern, wherein the wire is made of Au.

A thermal print head provided according to a fourth aspect of thepresent disclosure includes: a substrate; an electrode layer supportedby the substrate, and having a plurality of portions separated eachother; and a resistor layer having a portion configured to bridge theplurality of portions, wherein the electrode layer includes Ag as a maincomponent.

In some embodiments of the present disclosure, the electrode layer has afirst layer disposed on the substrate side, and a second layer laminatedon the first layer, and the second layer includes Ag particles.

In some embodiments of the present disclosure, the second layer includesa glass.

In some embodiments of the present disclosure, the first layer isthinner than the second layer.

In some embodiments of the present disclosure, the first layer includesPd.

In some embodiments of the present disclosure, the first layer and thesecond layer include Pd, and Pd content of the first layer is largerthan Pd content of the second layer.

In some embodiments of the present disclosure, the first layer includesan organic Ag compound.

In some embodiments of the present disclosure, the thermal print headincludes a glaze layer disposed between the substrate and the electrodelayer.

In some embodiments of the present disclosure, the thermal print headincludes a protection layer configured to cover the electrode layer andthe resistor layer.

In some embodiments of the present disclosure, the substrate is made ofAl₂O₃.

In some embodiments of the present disclosure, the electrode layerincludes a common electrode having a connecting portion and a pluralityof strip-shaped portions, and a plurality of individual electrodes,wherein the connecting portion extends in a primary scanning direction,the plurality of strip-shaped portions extend from the connectingportion in a second scanning direction, and each of the individualelectrodes has a strip-shaped portion extended in the second scanningdirection and located between adjoining strip-shaped portions, andwherein the resistor layer extends in the primary scanning direction tointersect with the plurality of strip-shaped portions of the commonelectrode and the strip-shaped portions of the plurality of individualelectrodes.

In some embodiments of the present disclosure, the electrode layerincludes a first thermal conduction layer and a second electricalconduction layer, wherein the first thermal conduction layer is directlycontacted with the resistor layer and includes Ag in a first ratio, andwherein the second electrical conduction layer is directly contacted tothe first thermal conduction layer and includes Ag in a second ratio,which is larger than the first ratio.

In some embodiments of the present disclosure, the first thermalconduction layer is mainly composed of an Ag—Pd alloy and the ratio ofAg is equal to or less than 80%, and the second thermal conduction layeris mainly composed of an Ag—Pd alloy and the ratio of Ag is equal to ormore than 80%.

In some embodiments of the present disclosure, the second electricalconduction layer is separated from the resistor layer.

In some embodiments of the present disclosure, the second electricalconduction layer is formed on the first thermal conduction layer, thefirst thermal conduction layer has an exposed portion exposed from thesecond electrical conduction layer, and the resistor layer is installedto contact with the exposed portion.

In some embodiments of the present disclosure, the second electricalconduction layer includes a body portion, and a separating portionlocated on an opposite side of the body portion with the resistor layerbeing interposed therebetween.

In some embodiments of the present disclosure, the electrode layer has aplurality of strip-shaped portions arranged along the primary scanningdirection, each of the stripe-shaped portions extends in the secondaryscanning direction, the exposed portion is installed on each of thestrip-shaped portions, and the separating portion is installed on afront end of each of the strip-shaped portions.

In some embodiments of the present disclosure, the second thermalconduction layer includes a first region formed on the second electricalconduction layer and a second region contacted with the resistor layer.

In some embodiments of the present disclosure, the second region of thefirst thermal conduction layer does not overlap with the secondelectrical conduction layer.

Other features and advantages of the present disclosure will become moreapparent from the detailed description made in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view showing a thermal print head according to a firstembodiment of the present disclosure.

FIG. 2 is an enlarged top view showing the thermal print head accordingto the first embodiment of the present disclosure.

FIG. 3 is a cross-sectional view along line in FIG. 2.

FIG. 4 is an enlarged cross-sectional view showing the thermal printhead according to the first embodiment of the present disclosure.

FIG. 5 is an enlarged cross-sectional photograph showing the thermalprint head according to the first embodiment of the present disclosure.

FIG. 6 is an enlarged cross-sectional view showing the thermal printhead according to the first embodiment of the present disclosure.

FIG. 7 is a cross-sectional view showing a substrate used in amanufacturing method of the thermal print head according to the firstembodiment of the present disclosure.

FIG. 8 is a cross-sectional view showing a state where a first layer ofan Ag paste layer is formed in the manufacturing method of the thermalprint head according to the first embodiment of the present disclosure.

FIG. 9 is a cross-sectional view showing a state where a second layer ofthe Ag paste layer is formed in the manufacturing method of the thermalprint head according to the first embodiment of the present disclosure.

FIG. 10 is a cross-sectional view showing a state where an electricconduction layer is formed in the manufacturing method of the thermalprint head according to the first embodiment of the present disclosure.

FIG. 11 is an enlarged cross-sectional view showing another embodimentof the thermal print head according to the first embodiment of thepresent disclosure.

FIG. 12 is an enlarged top-view showing a thermal print head accordingto a second embodiment of the present disclosure.

FIG. 13 is a cross-sectional view along line XIII-XIII in FIG. 12.

FIG. 14 is a diagram showing the main parts of the cross section alongline XIV-XIV in FIG. 13.

FIG. 15 is a diagram showing the main parts of the cross section alongline XV-XV in FIG. 13.

FIG. 16 is a diagram illustrating a material of an electrode layer inthe thermal print head shown in FIG. 12.

FIG. 17 is a diagram showing an example of the manufacturing method ofthe thermal print head shown in FIG. 12.

FIG. 18 is a diagram showing a step subsequent to the step shown in FIG.17.

FIG. 19 is a diagram showing a step subsequent to the step shown in FIG.18.

FIG. 20 is a diagram showing the main parts along line XX-XX in FIG. 19.

FIG. 21 is a diagram showing a step subsequent to the step shown in FIG.19.

FIG. 22 is a diagram showing a state after performing a patterning byetching after the state shown in FIG. 21.

FIG. 23 is an enlarged cross-sectional view showing a thermal print headaccording to a third embodiment of the present disclosure.

FIG. 24 is a diagram showing an example of a manufacturing step of thethermal print head shown in FIG. 23.

FIG. 25 is a diagram showing a step subsequent to the step shown in FIG.24.

FIG. 26 is a diagram showing a step subsequent to the step shown in FIG.25.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments, examples ofwhich are illustrated in the accompanying drawings. In the followingdetailed description, numerous specific details are set forth in orderto provide a thorough understanding of the present invention(s).However, it will be apparent to one of ordinary skill in the art thatthe present invention(s) may be practiced without these specificdetails. In other instances, well-known methods, procedures, systems,and components have not been described in detail so as not tounnecessarily obscure aspects of the various embodiments.

Some embodiments of the present disclosure will now be described indetail with reference to the drawings.

FIGS. 1 to 6 show a thermal print head according to a first embodimentof the present disclosure. The thermal print head A1 of the presentembodiment includes a substrate 1, a glaze layer 2, an electrode layer3, a resistor layer 4, a protection layer 5 and a drive IC 71. Thethermal print head A1 is assembled into a printer for printing thermalpaper, which may be a bar-code paper or receipts. Further, for the sakeof understanding, the protection layer 5 is omitted in FIGS. 1 and 2. Inthe figures, a primary scanning direction is an x direction, a secondaryscanning direction is a y direction, and a thickness direction of thesubstrate 1 is a z direction.

The substrate 1 is made of, for example, a ceramic such as Al₂O₃. Thethickness of the substrate 1 is, for example, about 0.6˜1.0 mm. As shownin FIG. 1, the substrate 1 is formed into an elongated rectangular shapeextending in the primary scanning direction x. In addition, thesubstrate 1 may have a configuration including a wiring substrate inwhich a base layer made of, for example, a glass epoxy resin and awiring layer made of, for example, Cu are laminated one above another.Further, a heat radiating plate made of metal such as A1, may beinstalled on the lower surface of the substrate 1. In the configurationhaving the wiring substrate, the substrate 1 and the wiring substrateare closely disposed on the heat radiating plate, and a wiring of thesubstrate 1 (or, IC connected to the wiring) and a wiring of the wiringsubstrate (or, IC connected to the wiring) are connected by, forexample, a wire bonding. Further, a connector 73 shown in FIG. 1 may beinstalled on the wiring substrate.

The glaze layer 2 is formed on the substrate 1, and is made of a glassmaterial such as an amorphous glass. A softening point of the glazelayer 2 is, for example, 800˜850 degrees C. The formation of the glazelayer 2 is performed by thick-film printing a glass paste and thensintering the thick-film printed glass paste. The glaze layer 2 may havea configuration including a protruding portion, which is extended in thex direction and is bulged in the z direction.

The electrode layer 3 is provided to define a route for applying anelectric current to the resistor 4. The electrode layer 3 is made of aconductor mainly composed of Ag. Further, in the present embodiment, theelectrode layer 3 includes a first layer 31 and a second layer 32 asshown in FIGS. 3 and 4. The electrode layer 3 is an example of the finewiring pattern according to the present disclosure.

The first layer 3 is formed on the glaze layer 2. The formation of thefirst layer 3 is performed by printing and sintering a paste including,for example, organic Ag compounds. The first layer 31 includes theorganic Ag compounds mainly composed of Ag. Also, the first layer 31includes Pd. The content of Pd is more than 0.1 wt % and is less than 30wt %. Further, the first layer 31 does not include a glass. Thethickness of the first layer 31 is, for example, 0.3 μm˜1.0 μm.

The second layer 32 is formed on the first layer 31. The formation ofthe second layer 32 is performed by printing and sintering, for example,an Ag paste for a thick-film print. The second layer 32 includes an Agpowder mainly composed of Ag. The Ag powder may have a spherical shapeor a flake shape. An average particle size of the Ag powder is, forexample, 0.1˜10 μm. Also, the second layer 32 includes a glass of, forexample, 0.5˜10 wt %. The glass is, for example, a borosilicate glass ora borosilicate lead glass. Also, the second layer 32 includes Pd. Forexample, the content of Pd is equal to or more than 0.1 wt % and is lessthan 30 wt %. The Pd content of the second layer 32 is smaller than thePd content of the first layer 31. The thickness of the second layer 32is, for example, 2-10 μm. A surface of the second layer 32 hasrelatively rough texture as the Ag powder is distributed.

As shown in FIG. 2, the electrode layer 3 includes a common electrode 33and a plurality of individual electrodes 36. The common electrode 33includes a plurality of strip-shaped portions 34 and a connectingportion 35. The connecting portion 35 is disposed near one end of thesubstrate 1 in the secondary scanning direction y. The connectingportion 35 extends in the primary scanning direction x and has astrip-like shape. Each of the strip-shaped portions 34 extends from theconnecting portion 35 in the y direction, and is arranged at a regularpitch along the x direction.

The plurality of individual electrodes 36 is provided for partiallyapplying the current to the resistor layer 4. Each of the individualelectrodes 36 has an electrical polarity, which is opposite to thecommon electrode 33. The individual electrodes 36 extend from theresistor layer 4 toward the drive IC 71. The individual electrodes 36are disposed along the primary scanning direction x. Each of theindividual electrodes 36 includes a strip-shaped portion 38, aconnecting portion 37 and a bonding portion 39. Each of the strip-shapedportions 38 extends in the secondary scanning direction y and is locatedbetween the adjoining two strip-shaped portions 34 of the commonelectrode 33. The width of the strip-shaped portion 38 of the individualelectrodes 36 and the width of the strip-shaped portion 34 of the commonelectrode 33 are equal to or less than 25 μm. The space between thestrip-shaped portion 38 of the individual electrode 36 and the adjacentstrip-shaped portion 34 of the common electrode 33 is equal to or lessthan 40 μm. The connecting portion 37 extends from the strip-shapedportion 38 toward the drive IC 71. The connecting portion 37 has a firstportion extended in the y direction and a second portion inclined withrespect to the y direction. The width of the most portion of theconnection portion 37 is equal to or less than 20 μm. The space betweenthe adjoining connecting portions 37 is equal to or less than 20 μm. Thebonding portion 39 is formed on one end of the individual electrodes 36in the y direction. The bonding portion 39 is boned with a wire 61 forconnecting the individual electrodes 36 and the drive IC 71. The bondingportion 39 of the adjoining individual electrodes 36 is staggered in they direction. Thus, while the width of the bonding portion 39 is largerthan the most portion of the connecting portion 37, it is possible toavoid the interference with each other. A portion interposed between theadjoining bonding portions 39 of the connecting portion 37 has thesmallest width in the individual electrodes 36. The width of the portionis equal to or less than 10 μm. Also, the space between the connectingportion 37 and the adjoining bonding portion 39 is equal to or less than10 μm. Thus, the common electrode 33 and the individual electrodes 36become the fine pattern having a relatively small line width and wiringspace.

FIG. 5 is a cross-sectional photograph of a portion of the thermal printhead A1 corresponding to FIG. 4. As shown in FIGS. 4 and 5, an uppersurface of the electrode layer 3 of the strip-shaped portion 34 or thestrip-shaped portion 38 of the individual electrode 36 has agently-sloping curved surface and does not have a sharp shape.

The resistor layer 4 is made of a material having a resistivity largerthan that of the electrode layer 3. Such material may be, for example, aruthenium oxide and the like. The resistor layer 4 is formed in theshape of a strip extending in the x direction. The resistor layer 4intersects with the strip-shaped portions 34 of the common electrode 33and the strip-shaped portions 38 of the individual electrodes 36. Theportions of the resistor layer 4 interposed between each of thestrip-shaped portions 34 and each of the strip-shaped portions 38 serveas heating portions. The heating portions are heated when the electriccurrent is partially applied by the electrode layer 3. Printing dots areformed by heating the heating portions.

The protection layer 5 is provided to protect the electrode layer 3 andthe resistor layer 5. The protection layer 5 is made of, for example, anamorphous material glass. However, the protection layer 5 exposes theregion including the bonding portions 39 of the individual electrodes36.

The drive IC 71 serves to selectively heat some of the resistor layer 4by selectively applying the electric current to the plurality ofindividual electrodes 36. The drive IC 71 includes a plurality of pads.FIG. 6 is an enlarged cross-sectional view in the y-z plane intersectingthe drive IC 71. As shown in FIGS. 2 and 6, the pads of the drive IC 71and the individual electrodes 36 are connected through a plurality ofwires 61. Each of the wires 61 are bonded to each of the pads and eachof individual electrodes 36. The wires 61 are made of Au. As shown inFIGS. 1 and 6, the drive IC 71 is covered with an encapsulation resin72. The encapsulation resin 72 is, for example, a black soft resin.Also, the drive IC 71 and the connector 73 are connected by a signalline (not shown).

Next, an example of a manufacturing method of the thermal print head A1will be described with reference to FIGS. 7 to 10.

First, the substrate 1 made of, for example, Al₂O₃ is prepared, as shownin FIG. 7. Next, the glaze layer 2 is formed by thick-film printing theglass paste on the substrate 1 and then sintering the printed glasspaste.

Next, the first layer 301 is formed, as shown in FIG. 8. The first layer301 is formed by thick-film printing a paste including an organic Agcompound. The paste including the organic Ag compound includes theorganic Ag compound, Pd and a resin. The resin content is, for example,60˜80 wt %.

Next, the second layer 302 is formed, as shown in FIG. 9. The secondlayer 302 is formed by thick-film printing an Ag paste for thethick-film print. The Ag paste for the thick-film print includes Agparticles, glass frits, Pd and a resin. The resin content is, forexample, 20˜30 wt %. The Ag paste layer 300 includes the first layer 301and the second layer 302.

Next, the conductor layer mainly composed of Ag is formed by sinteringthe Ag paste layer 300. Further, a conductor layer 3′ shown in FIG. 10is formed by a patterning process, for example, by etching the conductorlayer. The upper surface of the conductor layer 3′ has a sharp shape bythe etching. The conductor layer 3′ includes a first layer 31′ and asecond layer 32′. The first layer 31′ includes an organic Ag mainlycomposed of Ag, and the second layer 32′ includes the Ag particlesmainly composed of Ag. The resin, which is included to the first layer301 and the second layer 302, is evanesced by the above sinteringprocess. Because the first layer 301 includes more resin than the secondlayer 302, the first layer 31′ has the thickness thinner than the secondlayer 32′.

After the above processes, the resistor layer 4 and the protection layer5 are formed, and a mounting process of the drive IC 712 and a bondingprocess of the wires 61 are performed, so that the thermal print head A1is obtained. Further, in the sintering process for forming the resistorlayer 4 and the protection layer 5, the shape of the upper surface ofthe conductor layer 3′ is changed from the sharp shape to a curvedshape. As undergoing the shape change, the electrode layer 3 shown inFIGS. 3 and 4 is formed.

Next, the actions of the thermal print head A1 will be described.

In the present embodiment, the electrode layer 3 is made of a materialmainly composed of Ag. Therefore, for example, it is possible to reducethe manufacturing cost as compared with the configuration in which theelectrode layer 3 is made of a material mainly composed of Ag.

As the second layer 32 includes the Ag particles, the surface of thesecond layer 32 has relatively rough texture. Therefore, the contactarea of the second layer 32 and the resistor layer 4 is increased, andthe second layer 32 and the resistor layer 4 are easily attached. Thus,the contact resistance of the electrode layer 3 and the resistor layer 4can be reduced. Further, the wires 61 for connecting the individuallayer 36 and the drive IC 71 can be reliably bonded by the individualelectrodes 36. The attachment of the wires 61 made of Au and Ag aredifficult, and the bonding strength is reduced. However, an enoughbonding strength is obtained by roughly forming the surface of theboding portion 39.

As the second layer 32 includes the glass, the Ag particles supported bythe glass may easily distribute in a region near the surface of thesecond layer 32. It is suitable that the surface of the second layer 32has the rough texture.

The first layer 31 is thinner than the second layer 32, and includes theAg particles as well the organic Ag compound. This is similar to thefirst layer 31 of the conductor layer 3′ shown in FIG. 10. It issuitable that the first layer 31′ is finished with a more defined shapeby the patterning process using the etching and the like. According tothe present embodiment, the etching is performed for the conductor layerobtained by sintering the Ag paste layer 300 in which the first layer301 and the second layer 302 are laminated on above another. In thiscase, the patterning can be accurately performed upon the wholeconductor layer 3′ as the relatively thin first layer 31′ including theorganic Ag compound is formed. When the fine wiring pattern has thewiring width of 25 μm or smaller and the wiring space of 40 μm orsmaller in the strip-shaped portions 38 of the individual electrodes 36or the strip-shaped portion 34, and has the wiring width of 10 μm orsmaller, and the wiring space of 10 μm or smaller in the portioninterposed between the adjoining bonding portions 39 of the connectingportion 37, a precision of the patterning is not obtained, if the Agpaste is simply used. That is, there is a problem that the wiringsconnected with each other may be shorted in the etching, e.g., thewirings are disconnected by over-etching. In the present disclosure,although the fine wiring pattern is formed by using Ag, the patterningcan be accurately performed. According to the present embodiment, thefirst layer 31′ includes the organic Ag compound. However, the firstlayer 31′ may have other configuration including other material. Forexample, the paste including Ta₂O₃ may be used.

The first layer 31 includes Pd, and the content of Pd in the first layer31 is larger than the content of Pd in the second layer 32. In thiscase, it can be avoided that a resistance of the first layer 31 iswrongfully increased while the first layer 31 is thicker than the secondlayer 32. As a sheet resistance of the first layer 31 is reduced, a lowresistivity of the whole electrode layer 3 can be promoted. As the firstlayer 31 includes the organic Ag compound, the first layer 31 can bemade thinner and the sheet resistance can be made smaller. Further, asthe first layer 31 does not include the glass, it promotes that thesheet resistance is made smaller.

As described in the above, it is obtained that the connection with theresistor layer 4 is secured as the second layer 32 is formed to have arelatively rough surface texture. Although the material used tomanufacture the second layer 32 is the Ag paste for the thick-filmprinting, a material beside the above materials may be used tomanufacture the second layer 32. For example, the material may include aphotosensitive Ag paste.

A case where the photosensitive Ag paste is used as a material formanufacturing the second layer 32 will be described. The paste includesan Ag powder having an average particle size of, for example, 0.1˜10 μm.The Ag powder has a spherical shape or a flake shape. Further, the resincontent is about 20˜30 wt %. Metal components including Ag may beremained in the second layer 32 by exposing and then sintering thephotosensitive Ag paste. Also, the second layer 32 may be formed byexposing and hardening the photosensitive Ag paste. In the second layer32 formed by using the photosensitive Ag paste, the content of the glassis, for example, 0.5˜105, the thickness of the second layer 32 is, forexample, 2˜10 μm, and the content of Pd is more than 0.1 wt % and lessthan 30 wt %.

Further, an Ag nano paste may be used as a material for manufacturingthe second layer 32. The Ag nano paste includes Ag particles having theaverage particle size of, for example, 0.01˜0.5 μm. Also, the Ag nanopaste can be sintered at a lower temperature as compared with the Agpaste for the thick-film printing. The Ag nano paste has the resincontent of, for example, 20˜30 wt %. In the second layer 32 formed byusing the Ag nano paste, the content of the glass is, for example,0.5˜10%, the thickness of the second layer 32 is, for example, 0.5˜10μm, the content of Pd is 0.1˜30 wt %. When using the Ag nano paste, thesurface texture of the second layer 32 is made smoother than the case ofusing the Ag paste for the thick-film printing or the photosensitive Agpaste.

Further, although the drive IC 71 and the electrode layer 3 areconnected by the wire 61 is described in the present embodiment, aflip-chip connection between the drive IC 71 and the electrode layer 3may be performed by using the drive IC 71 having a solder bump. In thiscase, because the wires 61 made of Au are not used, the surface of thebonding portion 39 requires less roughness. Further, although all of theindividual electrodes 36 and the common electrode 33 are formed byprinting two layers according to this embodiment, some portions of theindividual electrodes 36 and the common electrode 33 may be formed tohave a two-layered structure.

FIGS. 12 to 26 show another embodiment of the present disclosure. Also,in these figures used in describing the manufacturing method, the samecomponents as described above will be designated by like referencesymbols.

FIGS. 12 to 16 show a thermal print head A2 according to a secondembodiment of the present disclosure. The configuration of the electrodelayer 3′ in the thermal print head A2 of the present embodiment isdifferent to the configuration of the electrode layer 3 in the thermalprint head A1 while other configurations in the thermal print head A2 ofthe present embodiment are similar to other configurations in thethermal print head A1. Further, for the sake of understanding, theprotection layer 5 is omitted in FIG. 12. In these figures, a primaryscanning direction is an x direction, a secondary scanning direction isa y direction, and the thickness direction of the substrate 1 is a zdirection.

As shown in FIG. 12, the shape of the electrode layer 3′ of the presentembodiment is substantially similar to that of the electrode layer 3 inthe thermal print head A1 when seen from a plane view. That is, theelectrode layer 3′ has the common electrode 33 and the plurality ofindividual electrodes 36 for the thermal print head A1. The commonelectrode 33 includes a plurality of strip-shaped portions 34 and aconnecting portion 35. The plurality of individual electrodes 36 arearranged along the primary scanning direction x. Each of the individualelectrodes 36 has a strip-shaped portion 38, a connecting portion 37 anda bonding portion 39.

The electrode layer 3′ of the present embodiment includes a low thermalconduction layer 310 directly connected with the resistor layer 4, and ahigh electrical conduction layer 320 directly connected with the lowthermal conduction layer 310. The most of the electrode layer 3′ has astructure in which the high electrical conduction layer 320 is laminatedon the low thermal conduction layer 310. As shown in FIGS. 14 and 15, aprotruding portion 21 is installed on the glaze layer 2, and someportions of the strip-shaped portions 34 and 38 extend to the protrudingportion 21. The high electrical conduction layer 320 is formed on thelow thermal conduction layer 310, and the low thermal conduction layer310 includes an exposed portion 310 a exposited from the high electricalconduction layer 320. The exposed portion 310 a is provided near an apexof the protruding portion 21. The resistor layer 4 is installed tocontact with the exposed portion 310 a.

As shown in FIG. 12, the high electrical conduction layer 320 includesmain body portion 320 a and a separating portion 320 b, which is locatedon an opposite side of the body portion 320 a while the resistor layer 4is interposed therebetween. Specifically, the body portion 320 a isinstalled on a region extended from a root of each of the strip-shapedportions 34 to one side of the resistor layer 4 in the direction y, theconnecting portion 35, a region extended from a root of the strip-shapedportion 38 to the other side of the resistor layer 5, the connectingportion 37 and the bonding portion 39. Meanwhile, the separating portion320 b is installed on a region extended from a front end of each of thestrip-shaped portions 34 to the other side of the resistor layer 4, anda region extended from a front end of each of the strip-shaped portions38 to the one side of the resistor layer 4. With this configuration, thehigh electrical conduction layer 320 is separated from the resistorlayer 4.

The strip-shaped portions 34 have a function for electrically connectingthe resistor layer 4 and the connecting portion 35. In the strip-shapedportion 34, the separating portion 320 b is located on an opposite sideof the connecting portion 35 while the resistor layer 4 is interposedtherebetween, and does not perform any function. Similarly, in thestrip-shaped portion 38, the separating portion 320 b is located on anopposite side of the connecting portion 37 and the bonding portion 39while the resistor layer 4 is interposed therebetween, and does notperform any function. The separating portion 320 is a portion formed asa result of the following manufacturing method.

The low thermal conduction layer 310 and the high electrical conductionlayer 320 are mainly composed of, for example, an alloy of Ag and Pd.FIG. 16 is a diagram illustrating a composition of an Ag—Pd alloy whichthe low thermal conduction layer 310 and the high electrical conductionlayer 320 are made of and shows a relationship between a ratio of Ag inthe Ag—Pd alloy and a thermal conductivity, and between the ratio of Agand an electrical resistance. As shown in FIG. 16, the thermalconductivity of the Ag—Pd alloy becomes a minimum when the ratio of Agis about 40%, and increases thereafter as the ratio of Ag increases. Thethermal conductivity is about 100 w/m·k when the ratio of Ag is 80%, andthe ratio of Ag increases thereafter as the ratio of Ag increases.Meanwhile, the resistance of the Ag—Pd alloy becomes a maximum when theratio of Ag is about 40%, and the ratio of Ag decreases thereafter asthe ratio of Ag increases. For example, when the ratio of Ag is 80%, theresistance of the Ag—Pd alloy is about 10 μΩ·cm. From the aboveproperties, the materials of the low thermal conduction layer 310 andthe high electrical conduction layer 320 are determined as thefollowing.

The low thermal conduction layer 310 is mainly composed of the Ag—Pdalloy that the ratio of Ag is equal to or less than 80%. Meanwhile, thehigh electrical conduction layer 320 is mainly composed of the Ag—Pdalloy that the ratio of the Ag is equal to or more than 80%. Accordingto the above configuration, the low thermal conduction layer 310 hasproperties that the thermal conductivity is equal to or less than 100w/m·k, and the heat is relatively difficult to be transmitted. Further,the high electrical conduction layer 320 has properties that theelectrical resistance is equal to or less than 10 μΩ·cm, and theelectrical conductivity is relatively excellent.

The process of forming the electrode layer 3 according to the presentembodiment can be performed in accordance with basically the sameprocess as the process of forming the electrode layer 3 in the thermalprint head A1. The difference between the process of forming theelectrode layer 3 in the thermal print head A2 and the process offorming the electrode layer 3 in the thermal print head A1 will bedescribed below with reference to FIGS. 17 to 22.

The low thermal conduction layer 310 is formed by printing andsintering, for example, a first paste material 311 including Ag in afirst ratio. The first paste material 311 is a mixture including, forexample, an organic Ag compound and an organic Pd compound. Whensintering the first paste material 311, Ag and Pd included in theorganic Ag compound and the organic Pd compound are alloyed. The firstratio is determined so that the ratio of Ag after alloying is equal toor less than 80%.

The high electrical conduction layer 320 is formed by printing andsintering a second paste material 321 including Ag in a second ratio,which is larger than the first ratio. The second paste material 321 is amixture including, for example, an organic Ag compound and an organic Pdcompound. When sintering the second paste material 321, Ag and Pdincluded in the organic Ag compound and the organic Pd compound arealloyed. The second ratio is determined so that the ratio of Ag afteralloying is equal to or more than 80%.

Although the first layer 301 and the second layer 302 are simultaneouslysintered in the process of manufacturing the thermal print head A1, thefirst paste material 311 and the second paste material 320 areindividually sintered in the present embodiment. Specifically, as shownin FIG. 17, a process of sintering the first paste material 311 isperformed after performing the process of printing the first pastematerial 311 on the glaze layer 2. As a result, as shown in FIG. 18, thefirst paste material 311 becomes the first layer 312. The first layer312 is mainly composed of the Ag—Pd alloy that the ratio of Ag is equalto or less than 80%.

After forming the first layer 312, the process of printing the secondpaste material 321 on the first layer 312 is performed as shown in FIGS.19 and 20. In this process, the second paste material 321 is printed soas to expose some portions of the first layer 312 at a position near thetop of the protruding portion 21 of the glaze layer 2. In FIG. 19, forthe sake of convenience, a diagonal line is referred to the region wherethe second paste material 321 is printed. As shown in FIG. 19, thesecond paste material 321 is printed so as to cover the glaze layer 2and the most of the first layer 312 except for the strip-shaped regionBe elongated in the x direction. In the strip-shaped region Be, theexposed portion 312 a of the first layer 312, which is exposed from thesecond paste material 321, becomes the exposed portion 310 asubsequently.

Next, a process of sintering the second paste material 321 is performedso as to form the second layer 322 shown in FIG. 21. The second layer322 is mainly composed of the Ag—Pd alloy that the ratio of Ag is equalto or more than 80%. The patterning by the etching process is performedthereafter. FIG. 22 shows a state after performing the patterning by theetching process. With the etching process, the first layer 312 becomesthe low thermal conduction layer 310, and the second layer 322 becomesthe high electrical conduction layer 320. Further, the most of thesecond layer 322 becomes the body portion 320 a, and a portion separatedfrom the body portion 320 a by the etching process becomes theseparating portion 320 b.

Specifically, the process of performing the etching process upon thefirst layer 312 and the second layer 322 includes a process of formingthe plurality of strip-shaped portions 34 and 38 arranged toward the xdirection. The strip-shaped portions 34 and 38 are formed so as toelongate in the y direction, respectively. Further, the strip-shapedportions 34 and 38 are formed so as to intersect the strip-shaped regionBe in the y direction, respectively. According to the manufacturingmethod, the separating portion 320 b remains in the front end of thestrip-shaped portions 34 and 38.

Further, in the manufacturing method of the thermal print head A2, theresistor layer 4 is formed so as to contact with the first layer 312exposed from the process of printing the second paste material 321, whenforming the resistor layer 4.

Next, the actions of the thermal print head A2 will be described.

The electrode layer 3 of the present embodiment is also made of amaterial mainly composed of Ag. Therefore, for example, it is possibleto reduce the manufacturing cost as compared with the configuration inwhich the electrode 3 is made of a material mainly composed of Au.

The electrode layer 3 in the present embodiment is configured by the lowthermal conduction layer 310 and the high electrical conduction layer320 having different Ag ratio. In the low thermal conduction layer 310having relatively small Ag ratio, the electrical resistance becomeslarge at one side that the thermal conductivity is low. Thus, it isundesirable that the electrode layer 3 is configured by only the lowthermal conduction layer 310. In the high electrical conduction layer320 having relatively large Ag ration, the thermal conductivity is alsohigh at one side that the electrical resistance is relatively small.From the viewpoint of suppressing the electrical resistance of theelectrode layer 3, it is desirable that the electrode 3 is configured bythe high electrical conduction layer 320. However, when the electrode 3is configured by only the high electrical conduction layer 320, there isa problem as described below.

Because of the thermal conductivity of the high electrical conductionlayer 320 is high, the heat emitted from the resistor layer 4 is easilyescaped to the high electrical conduction layer 320 when the electrodelayer 3 is configured by only the high electrical conduction layer 320.Therefore, there is the possibility that the time until accumulatingsufficient heat for performing the print upon the resistor layer 4becomes long, and the power consumption increases.

The configuration of the thermal print head A2 is intended to solve theproblem described above. According to this embodiment, the low thermalconduction layer 310 is directly contacted to the resistor layer 4, andthe high electrical conduction layer 320 is not directly contacted tothe resistor layer 4. Therefore, the heat emitted from the resistorlayer 4 is directly escaped to the low thermal conduction layer 310 thatthe thermal conductivity is relatively low, but is not directly escapedto the high electrical conduction layer 320. Thus, in the thermal printhead A2, the heat from the resistor layer 4 is hardly escaped, so thatthe time until accumulating sufficient heat for performing the printupon the resistor layer 4 and the power consumption can be reduced. Thisis desirable to reduce the power consumption of the thermal print headA2.

FIG. 23 shows a thermal print head according to a third embodiment ofthe present disclosure. The configuration of the electrode layer 3″ inthe thermal print head A3 of the present embodiment is different withthe configuration of the electrode layer 3 in the thermal print head A2,and other configurations in the thermal print head A3 of the presentembodiment are similar to other configurations in the thermal print headA2. FIGS. 24 to 26 show some portions of the manufacturing process ofthe thermal print head A3 shown in FIG. 23.

As shown in FIG. 23, according to the present embodiment, the lowthermal conduction layer 310 includes a first region 310A formed on thehigh electrical conduction layer 320, and a second region 310B directlyformed on the glaze layer 2 without overlapping with the high electricalconduction layer 320. The high electrical conduction layer 320 is formedon the glaze layer 2. The resistor layer 4 of the present embodiment isinstalled to contact with the second region 310B of the low thermalconduction layer 310.

When manufacturing the thermal print head A3 of the above configuration,a process of printing the first paste material 323 on the glaze layer 2is performed after forming the glaze layer 2, as shown in FIG. 24.Further, the first paste material of the present embodiment is similarto the second paste material 321 in the thermal print head A2. The firstlayer 324 is formed as sintering the first paste material 323 (see FIG.25) thereafter. The first layer 324 is mainly composed of the Ag—Pdalloy and the ratio of Ag is equal to or more than 80%.

Next, a process of printing the second paste material 313 to cover thefirst layer 324 is performed, as shown in FIG. 25. Further, the secondpaste material 313 of the present embodiment is similar to the firstpaste material 311 in the thermal print head A2. In this process, thesecond paste material 313 is also printed on some portions of the glazelayer 2. Therefore, the second paste material 313 includes a firstregion 313A printed on the first layer 324, and a second region 313Bwithout overlapping with the first layer 324. After printing the secondpaste material 313, the sintering is performed upon the second pastematerial 313, so that the second layer 314 shown in FIG. 26 is formed.The second layer 314 is mainly composed of the Ag—Pd alloy and the ratioof Ag is equal to or more than 80%. The second layer 314 also includes afirst region 314A formed on the first layer 324 and a second region 314Bwithout overlapping with the first layer 324. The patterning by theetching process is performed upon the first layer 324 and the secondlayer 314 thereafter. After the etching process, a lower portion of thefirst region 314A becomes the first region 310A, and a lower portion ofthe second region 314B becomes the second region 310B.

The thermal print head A3 of the present embodiment also have aconfiguration that the high electrical conduction layer 320 havingrelatively high thermal conductivity is not directly contacted with theresistor layer 4, so that the heat from the resistor layer 4 is hardlyescaped. Therefore, it is suitable to reduce the power consumption ofthe thermal print head A3 as the thermal print head A2.

The manufacturing method of the fine wiring pattern, the fine wiringpattern, and the thermal print head according to the present disclosureare not limited to the above embodiments. Modifications and variationscan be made to the specific construction of the manufacturing method ofthe fine wiring pattern, the fine wiring pattern, and the thermal printhead according to the present disclosure.

With the above-described configuration, the electrode layer is made of amaterial mainly composed of Ag. Therefore, it is possible to reduce themanufacturing cost as compared with the configuration in which theelectrode layer is made of a material mainly composed of Au.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the embodiments herein may be embodiedin a variety of other forms. Furthermore, various omissions,substitutions and changes in the form of the embodiments describedherein may be made without departing from the spirit of the inventions.The accompanying claims and their equivalents are intended to cover suchforms or modifications which would fall within the scope and spirit ofthe inventions.

What is claimed is:
 1. A thermal print head, comprising: a substrate; anelectrode layer supported by the substrate, and including a plurality ofportions separated each other, the electrode layer having a first layerand a second layer; and a resistor layer having a portion configured tobridge the plurality of portions, wherein the first layer is in directcontact with the resistor layer and includes silver.
 2. The thermalprint head of claim 1, wherein the second layer includes a glass.
 3. Thethermal print head of claim 1, wherein the first layer is thinner thanthe second layer.
 4. The thermal print head of claim 3, wherein thefirst layer includes palladium.
 5. The thermal print head of claim 3,wherein the first layer and the second layer include palladium, and apalladium content of the first layer is larger than a palladium contentof the second layer.
 6. The thermal print head of claim 1, wherein thefirst layer includes an organic silver compound.
 7. The thermal printhead of claim 1, comprising: a glaze layer disposed between thesubstrate and the electrode layer.
 8. The thermal print head of claim 1,comprising: a protection layer configured to cover the electrode layerand the resistor layer.
 9. The thermal print head of claim 1, whereinthe substrate is made of aluminum-oxide.
 10. The thermal print head ofclaim 1, wherein the electrode layer includes a common electrode havinga connecting portion and a plurality of strip-shaped portions, and aplurality of individual electrodes, wherein the connecting portionextends in a primary scanning direction, the plurality of strip-shapedportions extend from the connecting portion in a second scanningdirection, and each of the individual electrodes has a strip-shapedportion extended in the second scanning direction and located betweenadjoining strip-shaped portions, and the resistor layer extends in theprimary scanning direction to intersect with the plurality ofstrip-shaped portions of the common electrode, and the strip-shapedportions of the plurality of individual electrodes.
 11. The thermalprint head of claim 1, wherein the first layer in direct contact withthe resistor layer includes silver in a first ratio, and the secondlayer is in direct contact with the first thermal conduction layer andincludes silver in a second ratio, which is larger than the first ratio.12. The thermal print head of claim 11, wherein the first layer is madeof a silver-palladium alloy and the ratio of silver is equal to or lessthan 80%, and the second layer is made of a silver-palladium alloy andthe ratio of silver is equal to or more than 80%.
 13. The thermal printhead of claim 12, wherein the first layer includes a first region formedon the second layer and a second region contacted with the resistorlayer.
 14. The thermal print head of claim 13, wherein the second regionof the first layer does not overlap with the second layer.
 15. Thethermal print head of claim 12, wherein the second layer is separatedfrom the resistor layer.
 16. The thermal print head of claim 15, whereinthe second layer is formed on the first layer, wherein the first layerhas an exposed portion, and wherein the resistor layer is installed tocontact the exposed portion.
 17. The thermal print head of claim 16,wherein the second layer includes a body portion, and a separatingportion located on an opposite side of the body portion with theresistor layer being interposed between the body portion and theseparating portion.
 18. The thermal print head of claim 17, wherein theelectrode layer has a plurality of strip-shaped portions arranged alongthe primary scanning direction, each of the stripe-shaped portionsextends in the secondary scanning direction, and the exposed portion isinstalled on each of the strip-shaped portions, and the separatingportion is installed on a front end of each of the strip-shapedportions.